1. Field of the Invention
The present invention relates to image data compression devices, more particularly, to an image data compression device for compressing the image data to lower than or equal to a prescribed capacity value.
2. Description of the Related Art
With advancement in recent network technology and the widespread use of personal computers and portable telephones, data communication, especially, data communication using electronic mails between terminals is being carried out on a daily basis. In addition to text data such as mail main text, various forms of files such as images, voices, video files and the like can be attached to the electronic mail, and such files can be transmitted to other terminals.
However, if the number of attached files is great and the capacity is large, there requires tremendous communication time and communication cost, which may impose excessive load on the network, server, and the receiver terminal as well. Further, other important electronic mails may not be received if such large capacity electronic mail is being received. Thus, an upper limit value is generally set to the data size of the file that can be received in electronic mail. Particularly, since the memory capacity of the telephone itself is extremely small in portable telephones, the capacity of the transmittable and receivable electronic mail is limited to be extremely small.
Therefore, reducing the data capacity of the file itself that is transmitted and received during communication is being considered, which technique is disclosed in the following Patent Literature. Japanese Laid-Open Patent Publication No. 2003-281063 (Patent Literature 1) discloses a technique of reducing the data size by compressing or deleting the image data attached to the electronic mail until the upper limit value is not exceeded when the data size of the electronic mail exceeds a prescribed upper limit value.